CVE-2020-36477

Severity: medium (CVSS 5.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-08-23 · updated 2026-06-17
Weakness: CWE-295

Description

An issue was discovered in Mbed TLS before 2.24.0. The verification of X.509 certificates when matching the expected common name (the cn argument of mbedtls_x509_crt_verify) with the actual certificate name is mishandled: when the subjecAltName extension is present, the expected name is compared to any name in that extension regardless of its type. This means that an attacker could impersonate a 4-byte or 16-byte domain by getting a certificate for the corresponding IPv4 or IPv6 address (this would require the attacker to control that IP address, though).

Affected products

mbedtls: before 2.24.0 — fixed in 2.24.0

How to fix

Upgrade to a fixed version: mbedtls 2.24.0. Check the vendor advisory for mitigations.

References

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